This invention relates generally to crop harvesting and threshing machines, more commonly known as combines, and more particularly to the trapdoor area in the infeed housing wherein stones and other foreign non-crop objects are ejected from the infeed housing prior to their entering the threshing and separating apparatus of the combine. Specifically, the invention is concerned with the seal that exists between the sidewalls of the infeed housing and the trapdoor to prevent the loss of crop material which might fall therebetween during the normal field operations of the combine.
In the prior conventional types of combines, stone traps were routinely provided to separate out large hard objects or stones that generally were greater than three or four inches in size. The stone traps provided in the conventional combines were utilized generally in two types of stone ejecting systems. The passive type of stone ejecting system employed a stone trap with a space or gap between the top of the crop elevator or conveyor within the infeed housing and the base unit threshing apparatus. In this type of an ejecting system hard objects or stones were conveyed upwardly along with the crop material from the header through the infeed housing towards the threshing apparatus. When the crop material passed over the gap, stones by their very weight would fall down through the gap into the stone trap. Those stones that were carried along with the crop material past the stone trap were passed into contact with the threshing cylinder, which generally was rotatably mounted transversely to the longitudinal axis of the combine. If the hard objects or stones were of sufficient size so that they would not easily pass between the threshing cylinder and the threshing concaves, they would be thrown backwardly by the rotation of the cylinder into the gap or space. Thus, this particular cooperation between the threshing cylinder and the stone trap created an almost natural stone ejecting system for conventional combines. Even if a stone did pass into the threshing cylinder it made only one pass about the cylinder and across the underlying concave, usually doing minimal damage to the threshing apparatus before it was passed through and ejected from the combine.
The second type of stone ejecting system generally employed an active system which utilized some sort of a detecting system to detect the presence of a stone or other non-frangible object. Typically an electronic sensor, such as an acoustic transducer usually in the form of a piezoelectric disc, is mounted in a sensing plate and is used in conjunction with a stone trap. The electronic sensor responded to the characteristics of the sound, such as the amplitude and frequency, that an impacting stone generated in the sensing bar. This signal would then be transferred through an electronic circuit that filtered out the range within which the amplitude and frequency was characteristic of stones. Within this characteristic spectral range the electronic circuit automatically activated a latch releasing mechanism on a door along the bottom of the infeed housing that would pivot open to permit the stones or hard objects to be ejected from the feeder house, along with a small amount of crop material.
An alternate type of active stone ejecting system utilized a pinch roll rotatably mounted in the infeed housing at a predetermined distance above the trapdoor. When a stone of sufficient size was carried by the crop elevator between the pinch roll and the trapdoor into compressive engagement therewith, the rotation of the pinch roll exerted a downward force through the stone against the trapdoor. The trapdoor was spring loaded closed so that above a predetermined pressure the door would be forced open, thereby causing the stone to be directed downwardly and out of the infeed housing through the opening created by the opened trapdoor.
Of those type of active stone ejecting systems which utilize a door or opening in the infeed housing to allow stones or other foreign objects to pass therethrough, normally some type of a sealing material is used between the door and the bottom surface of the infeed housing to prevent the loss of crop material which can escape therebetween. Early attempts to utilize a trapdoor type of structure without any sealing material resulted in unacceptable losses of crop material as it escaped through the space between the edges of the trapdoor and infeed housing. When sealing materials were utilized between the edges of the trapdoor and the opposing sidewalls of the infeed housing to eliminate this loss they were found to be generally acceptable, but were typically composed of a pliant material such as rubber. After extended periods of use this pliant sealing material would crack or become torn, thereby permitting crop material once again to escape at the damaged area, in addition to necessitating periodic replacement. The periodic replacement of the sealing material obviously added additional costs and utilized additional time to maintain the combine in its proper operational condition.
The foregoing problems are solved in the design of the combine infeed housing comprising the present invention by providing an improved seal for the stone trapdoor and the opposing sidewalls of the infeed housing which is formed directly into the opposing sidewalls.